With a savings goal set at 25 % for the Danish waste water industry, optimizing all parts of the operation, so even the aeration, is of the highest importance. The Waste Water Treatment Plant in Skanderborg, Danmark, recently replaced one of its 75 kW lobe blowers with a new 55 kW Atlas Copco ZS screw blower and were able to reduce their energy consumption by 31%.

Up to 70 % of the energy consumed by a Waste Water Treatment Plant (WWTP) consists of low pressure aeration of the waste water, why savings in this part of the process is of paramount importance. Atlas Copco’s ZS screw blowers are on average 30 % more energy efficient than lobe blowers. This has been proven by independent tests by TÜV and by WWTP’s in Scandinavia.

“Skanderborg WWTP had problems with their aeration using lobe blowers so we suggested that they should try the Atlas Copco ZS blow¬ers”, says Flemming Broksø, Sales Engineer at Atlas Copco Compressor Technique Scandinavia.

“We chose Atlas Copco as supplier of our new blower as they showed us possible energy savings of 30 % compared to our old lobe blower” says Ivan Andersen at Skanderborg WWTP.

During August every year in Skanderborg the traditional Summer Festival takes place. This is the time of the year when the work load is at its highest for Skanderborg WWTP, and where the blowers operate on maximum capacity. During the festival, a test was carried out by Skander¬borg WWTP comparing the energy consumption of the two identical aeration process lines.

Both lines are equipped with two blowers each – one variable speed drive and one fixed speed. The operations are set up so that the variable speed drive blowers function as the primary blowers and the fixed speed blowers come in when the demand for low pressure air increases.
Open table

Line 1

Line 2

1 75 kW lobe blower, variable speed drive

1 Atlas Copco ZS55VSD-700 screw blower, variable speed drive

1 75/62 kW (dual speed) lobe blower, fixed speed

1 75/62 kW (dual speed) lobe blower, fixed speed

The result

The result

Total energy consumption: 19 989 kWh

Total energy consumption: 14 492 kW

The figures show a total saving of energy for Line 2 – including the Atlas Copco ZS screw blower – at 31 %.

“The Atlas Copco ZS screw blower is working really well, better than expected. It runs smooth and has, besides replacing a bigger lobe blower, lowered the amount of time that the fixed speed lobe blower has to support the VSD blower in its aeration process line”, Ivan Andersen says.

“This has given us big energy sav¬ings and we are calculating a pay¬back time of the ZS blower as low as only 16 months. We also made it through the Skanderborg Summer Festival without any downtime, and it runs much more silent than the old lobe blower”, he concludes.

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Atlas Copco is an industrial group with world-leading positions in compressors, expanders and air treatment systems, construction and mining equipment, power tools and assembly systems. With innovative products and services, Atlas Copco delivers solutions for sustainable productivity. The company was founded in 1873, is based in Stockholm, Sweden, and has a global reach spanning more than 170 countries. In 2011, Atlas Copco had 37 500 employees and revenues of BSEK 81 (BEUR 9).

Atlas Copco’s Compressor Technique business area provides industrial compressors, gas and process compressors and expanders, air and gas treatment equipment and air management systems. It has a global service network and offers specialty rental services. Compressor Technique innovates for sustainable productivity in the manufacturing, oil and gas, and process industries. Principal product development and manufacturing units are located in Belgium, Germany, the United States, China and India.